DESCRIPTION: (Taken from the Abstract) HIV and SIV virions shed a significant fraction of their gp120 glycoproteins. The immune system responds to these envelope fragments, creating non-neutralizing antibodies that are usually incapable of binding to the native envelope glycoprotein complex. The goal of this initial independent research project is to generate and test the comparative imunogenicity of non-infectious virus-like particles (VLP) that contain disulfide-stabilized envelope glycoprotein complexes (SOS proteins). The envelope glycoprotein mutants that will be expressed on these particles have a disulfide bond between the gp120 and gp41 subunits which prevent gp120 shedding. These SOS envelope glycoproteins mimic the antigenic configuration of the native complex. Thus, their presentation on a multivalent array of VLPs might be advantageous enabling the SOS-VLPs to be a potential component in a combination vaccine. Two Specific Aims are proposed: Specific Aim 1: The SOS mutations will be introduced into the SIVmne envelope (Env) gene to create a disulfide bond between the gp120 and gp41 subunits. The immunochemical, biophysical and morphological properties of the resulting SOS-VLPs will be compared to wild type VLPs. An emphasis will be to determine the glycoprotein retention on particles as well as assessment of its antigenic configuration. Specific Aim 2: Test the immunogenicity of the SOS-VLPs in rabbits in comparison with wild type VLPs and soluble SOS gp140 proteins. The most important end point will be to measure the breadth and potency of neutralizing antibodies against matched virus isolates as well as against more diverse isolates providing an indication of worth of VLP immunogens as vaccine components. If SOS-VLPs seem promising, the investigator proposes to generate a recombinant vaccinia capable of expressing VLPs. The SOS-VLPs then will be used in a prime-boost vaccination and SIVmne challenge studies in macaques. Ultimately, the information obtained in these studies will be applied to those to make HIV-1, SOS-VLPs as components of a combination vaccine against HIV-1 infection.